THE MULTI-STOREY BUILDINNGS STEEL FRAMES VITALITY IN THE FIRE INCREASING

Abstract

In the article multi-story buildings steel frames in the fire before and after the first destruction is investigated, the frames vitality in the fire is investigated. It is emphasized on the relevance of the research during the war of the russian federation against Ukraine. An overview of previous domestic and foreign scientists’ studies, devoted to the multi-story buildings steel frames vitality, in particular in a fire. The frame model for research was selected and simplifications was required in the study for the clarity of comparisons in research. There were compared different mechanisms of multi -story buildings steel frames collapse in a fire. It is proved that with the first destruction in the steel frame beam the vitality loss time will be longer than with the column first destruction. Various measures vitality increasing frames are considered and investigated. Outrigger systems were investigated as a measure vitality increasing, and their impact on the forces distribution in the frame during heating of frame elements under the action of temperature loads from a fire. The dependence of various measures vitality increasing of multi-story buildings steel frames in the fire from the frame geometric sizes is established. It is established that the load -bearing capacity factor at the fire beginning in the most loaded column should be smaller than the most loaded beams. It is proved that the difference between the initial load-bearing capacity factor in the beam and column that necessary to increase the vitality loss time, is different for different ratios of beam span to the column height. It is revealed that the frame elements cross-sections shape affects its vitality in the fire. The importance of the limited plate deformations development in the frame elements cross-sections is emphasized. Recommendations for civil engineers to enhance the of multi-story buildings steel frames vitality in a fire are formed.